Aluminum beam leaded chips,substrates and crossovers: A single metal system

A single metal system for beam-leaded chips, substrates and crossovers has been shown to be feasible using aluminum. Beams were formed on both ceramic substrates with holes tented with Riston (a sheet photoresist) and on silicon wafers by vacuum evaporation of aluminum from multiple tungsten filaments, and subsequent delineation and etching using photolithographic techniques. The chips with beams were separated from the wafer by anisotropic etching, and the tenting material removed from the ceramic by dissolution in appropriate solvents or an oxygen plasma. Beams were formed on polyimide sheet by photolithographically etching an adhesiveless laminate of aluminum on polyimide. Actual working samples have been fabricated of aluminum beam leads on ceramic and plastic substrates, aluminum beam leaded crossovers on ceramic, aluminum crossovers on plastic using multilayers and aluminum beam leaded silicon chips. Standard integrated circuit chips have been ultrasonically bonded into these substrates and the beam leaded chips have been ultrasonically bonded to an aluminum coated substrate. Environmental physical tests have shown the beam leads and crossovers to be rugged.